1. Field
The following description relates to a rechargeable secondary battery, and more particularly to a rechargeable secondary battery with improved safety against puncture and collapse.
2. Description of Related Art
Lithium ion secondary batteries are widely used as a power source for small electronic devices such as notebook computers and cellular phones. In addition, because lithium ion secondary batteries have high output density, high capacity, and are light weight, they are also being used in hybrid and electric automobiles.
Lithium ion secondary batteries used as a power source of automobiles should satisfy safety and reliability requirements under severe conditions. There are a plurality of test categories for safety, among which, three of the most extreme test categories include puncture, collapse, and overcharge.
The puncture and collapse tests are performed to estimate secondary battery related damage in the event of a car accident and thus are very important test categories for safety. Specifically, in nail puncture tests, such as a nail penetration test, and collapse tests, the battery should not excessively increase in temperature after puncture or collapse.